This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
Xiaomei Yue, Mariana Kikuti, Marcello Melini, Carlos Lora, Robert Langenhorst, Scott Dee, and Cesar Corzo take a look at the impact of air filtration on PRRS occurrence in today’s Science Page.
Key points:
- Air filtration significantly reduces PRRS incidence in sow herds based on 16 years of field data.
- Both year-round and partial-year filtration, as well as positive and negative-pressure systems, provide protective effects.
Introduction
Porcine reproductive and respiratory syndrome (PRRS) remains a major threat to swine health, welfare and economic sustainability. Airborne transmission of PRRS virus facilitates rapid spread, particularly in regions with high pig density. Air filtration has emerged as a core preventive biosecurity intervention, yet long-term field evidence accounting for ventilation type, filtration duration, and regional pig density is limited. This study aimed to quantify the effect of filtration approach (year-round vs. partial-year) and air filtration ventilation pressure type (positive vs. negative) on PRRS occurrence across U.S. sow herds.
Materials and Methods
Longitudinal data spanning 2009–2024 was collected from the Morrison Swine Health Monitoring Project (MSHMP), the final analyzed data included farms from 25 production systems in 12 states, representing ~1.6 million sows in 245 non-filtered and 178 filtered farms. Generalized additive models with a negative binomial distribution assessed the effect of filtration on the number of PRRS outbreaks per farm, incorporating Gaussian process smooths to account for spatial autocorrelation. Sub-analyses evaluated temporal trends and differences between filtration approaches and pressure types.
Results
The annual cumulative incidence of farms with different filtration approach and ventilation pressure is shown in Figure 1A and 1B, respectively. While this descriptive summary offers useful context, the confounder-adjusted generalized additive models showed that filtered herds consistently exhibited lower PRRS incidence than non-filtered herds after accounting for regional density. Compared to non-filtered farms, those with year-round and partial-year air filtration showed significantly lower PRRS incidence rates, with 0.494 times (p < 0.001) and 0.502 times (p = 0.006) the incidence rate of non-filtered farm, respectively. Farms with negative-pressure filtration had 0.492 times (p < 0.001) the incidence rate, while positive-pressure farms showed 0.416 times (p < 0.001) the incidence rate of non-filtered farms. No conclusive differences were observed between year-round and partial-year filtration or between positive- and negative-pressure systems, likely due to limited sample sizes.
Discussion
This study offers valuable evidence on the effects of different air filtration approaches on PRRS occurrence while accounting for regional disease burden and ventilation pressure. These findings demonstrate a significant and sustained protective effect of air filtration as an important component of biosecurity measures on PRRS occurrence. Effectiveness depends on system design, maintenance, and regional herd density. Positive-pressure systems offer structural advantages but require higher operational and construction standards, whereas negative-pressure systems are easier to retrofit. Partial-year filtration remains effective but may require careful seasonal planning. These findings offer field-based evidence to guide investment in filtration systems and inform tailored biosecurity strategies, optimizing disease prevention across diverse production environments.
Read the full paper: https://doi.org/10.1016/j.animal.2026.101834